1. Field of the Invention
This invention relates generally to method for whitening human teeth, and more particularly, to a method of whitening teeth by sequentially first applying to the teeth an alkaline rinse followed by brushing with a peroxide containing dentifrice.
2. The Prior Art
A tooth is comprised of an inner dentin layer and an outer hard enamel layer that is the protective layer of the tooth. The enamel layer of a tooth is naturally an opaque white or slightly off-white color. It is this enamel layer that can become stained or discolored. The enamel layer of a tooth is composed of hydroxyapatite mineral crystals that create a somewhat porous surface. It is believed that this porous nature of the enamel layer is what allows staining agents and discoloring substances to permeate the enamel and discolor the tooth.
Many substances that a person confronts or comes in contact with on a daily basis can "stain" or reduce the "whiteness" of one's teeth. In particular, the foods, tobacco products and fluids such as tea and coffee that one consumes tend to stain one's teeth. These products or substances tend to accumulate on the enamel layer of the tooth and form a film over the teeth. These staining and discoloring substances can then permeate the enamel layer. This problem occurs gradually over many years, but imparts a noticeable discoloration of the enamel of one's teeth.
Means known to the art to effect whitening of teeth include the application, as by brushing, to the teeth of peroxide containing dentifrice compositions of the type disclosed in U.S. Pat. No. 5,256,402 and U.S. Pat. No. 5,814,309.
The aqueous dentifrice compositions disclosed these patents contain a urea or hydrogen peroxide compound, an alkali pyrophosphate salt and an abrasive material. Although such peroxide dentifrice compositions of the prior art are effective in whitening teeth, the art continuously seeks means to effect even greater tooth whitening efficacy.